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| United States Patent |
5,246,569
|
|
Heinerman
, et al.
|
September 21, 1993
|
Process for the hydrodesulfurization of light hydrocarbon feeds
Abstract
A process for the catalytic hydrodesulfurization of hydrocarbon- containing
feeds using a catalyst of a phosphorus component, a cobalt component and a
Group VIB metal component on an alumina carrier.
| Inventors:
|
Heinerman; Jacobus J. L. (PG Amsterdam, NL);
van Hengstum; Antonius J. (GE Deventer, NL);
de Mind; Menno (AB Amsterdam, NL)
|
| Assignee:
|
Akzo N.V. (Arnhem, NL)
|
| Appl. No.:
|
739940 |
| Filed:
|
August 2, 1991 |
Foreign Application Priority Data
| Current U.S. Class: |
208/216R; 208/216PP |
| Intern'l Class: |
C10G 045/08 |
| Field of Search: |
502/211
208/216 R,216 PP
|
References Cited
U.S. Patent Documents
| 3232887 | Feb., 1966 | Pessimisis | 502/211.
|
| 3749664 | Jul., 1973 | Mickelson | 208/254.
|
| 3840472 | Oct., 1974 | Colgan et al. | 252/435.
|
| 4014821 | Mar., 1977 | Hamner | 208/216.
|
| 4028227 | Jun., 1977 | Gustafson | 208/216.
|
| 4154812 | May., 1979 | Sanchez et al. | 423/616.
|
| 4392985 | Jul., 1983 | Millman | 252/435.
|
| 4444905 | Apr., 1984 | Pessimisis | 502/211.
|
| 4686030 | Aug., 1987 | Ward | 208/216.
|
| 4716141 | Dec., 1987 | Kemp | 502/211.
|
| 4879265 | Nov., 1989 | Simpson et al. | 502/211.
|
| 4941964 | Jul., 1990 | Dai et al. | 208/216.
|
| Foreign Patent Documents |
| 0164162 | Dec., 1985 | EP.
| |
| 0244106 | Nov., 1987 | EP.
| |
| 0126250 | Dec., 1987 | EP.
| |
| 0112667 | Mar., 1988 | EP.
| |
| 0266009 | May., 1988 | EP.
| |
| 0309046 | Mar., 1989 | EP.
| |
| 2055602 | Mar., 1981 | GB.
| |
Other References
M. DeWind, et al. (Akzo Chemicals) "Upflow versus Downflow Testing of
Hydrotreating Catalysts," Applied Catalysis vol. 43, pp. 239 ff (1988).
Arie de Bruijn, et al. (Akzo Chemie Nederland b.v.) "Effect of the
Noncylindrical Shape of Extrudates on the Hydrodesulfurization of Oil
Fractions," Ind. Eng. Chem Process Des. Dev. vol. 20, pp. 40 ff (1981).
Arie De Bruijn, "Testing of hds Catalysts in Small Trickle Phase Reactors"
Proc. 6th Int. Congr. Catal. vol. 2, London 1976 (eds. G. C. Bond et al.),
paper B34 (pp. 951-964.
Kirk-Othmer's "Encyclopedia of Chemical Technology," Third Ed., vol. 2, pp.
218-228 (John Wiley & Sons, N.Y. 1978).
|
Primary Examiner: Shine; W. J.
Attorney, Agent or Firm: Poole; James K., Morris; Louis A.
Claims
We claim:
1. A process for the catalytic hydrodesulphurization of
hydrocarbon-containing feeds having a metals content of Ni plus V not
exceeding 15 ppm and a boiling point range wherein more than 50 volume
percent of the feed boils below 600.degree. C., comprising contacting said
feeds under hydrodesulphurization conditions with a catalyst composition
containing a porous inorganic oxide carrier comprising at least one
transition alumina, a comparatively low proportion of a phosphorus
component and comparatively high proportions of a cobalt component and a
Group VIB metal component, wherein said phosphorus component content,
calculated as P.sub.2 O.sub.5, is in the range of from about 2 to about 28
mmoles, said cobalt component content, calculated as CoO, is in the range
of from about 60 to about 133 mmoles and said Group VIB metal component
content, calculated as trioxide, is in the range of from about 132 to
about 208 mmoles, all calculated on the basis of 100 grams of said
catalyst composition.
2. The process of claim 1 wherein said catalyst composition has a specific
surface area of at least about 100 m.sup.2 /g and a pore volume in the
range of from about 0.25 to about 1.3 ml/g.
3. The process of claim 2 wherein less than 5 percent of said catalyst's
pore volume is contained in pores having a diameter of greater than 25 nm.
4. The process of claim 1 wherein said Group VIB metal is molybdenum.
5. The process of claim 4 wherein said catalyst composition contains from
19 to about 23 weight percent molybdenum, from 4.5 to about 6 weight
percent cobalt and from 0.3 to about 3 weight percent phosphorus.
6. The process of claim 1 wherein the median pore diameter of said catalyst
composition has a value in the range of from about 5 to about 15 nm.
7. The process of claim 1 wherein said catalyst composition is prepared by
a process in which a chemical precursor of the transition alumina is
shaped, the shaped material is subjected to at least one calcining step in
order to form transition alumina, and the precursors of the phosphorus
component and the metal components are deposited on the carrier material
prior to, during and/or after the shaping step, with the proviso that the
cobalt component precursor is deposited after the forming of the
transition alumina.
Description
REFERENCES TO RELATED APPLICATIONS
The present application for patent is entitled to the benefit of an earlier
filing date in a foreign country under 35 U.S.C. 119, based on priority
application Ser. No. 9001762, The Netherlands, Aug. 3, 1990, which is
hereby incorporated by reference.
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a catalyst composition suitable for hydrotreating,
more particularly for hydrodesulphurizing hydrocarbon-containing feeds.
The invention further relates to processes for the preparation and use of
the catalyst composition.
Background of the Invention
In general, the object of catalytically hydrotreating
hydrocarbon-containing feeds is the complete or partial removal of
impurities. Common impurities are sulphur compounds and nitrogen
compounds. The at least partial removal of such impurities from a feed
will ensure that, when the final product is burned, fewer sulphur oxides
and/or nitrogen oxides damaging to the environment will be released In
addition, sulphur compounds and nitrogen compounds are toxic to many of
the catalysts employed in the oil industry for converting feeds into
ready-for-use products. Examples of such catalysts include cracking
catalysts, hydrocracking catalysts, and reforming catalysts. It is
therefore customary for feeds to be subjected to a catalytic
hydrotreatment prior to their being processed in, say, a cracking unit.
Catalytic hydrotreatment implies contacting a feed with hydrogen at
elevated temperature and pressure in the presence of a hydrotreating
catalyst. In this process the sulphur compounds and nitrogen compounds
present in the feed are converted into readily removable hydrogen sulphide
and ammonia.
In general, hydrotreating catalysts are composed of a carrier having
deposited thereon a group VIB metal component and a group VIII metal
component The most commonly employed group VIB metals are molybdenum and
tungsten, while cobalt and nickel are the conventional group VIII metals.
As a rule, such catalysts are prepared by impregnating a carrier with an
aqueous solution of compounds of the metals in question, followed by a
drying step and a calcination step. The impregnating solution will usually
contain a phosphorus compound, such as phosphoric acid, to enhance the
stability of the solution. See, e.g., U.S. Pat. No. 3,840,472, in which it
is recommended to dissolve first particular nickel salts or cobalt salts
and then molybdenum trioxide in aqueous phosphoric acid, such that
specific concentrations of the three components in the final solution are
obtained.
Over the years many different ways of improving the action of
phosphorus-containing catalysts in hydrodesulphurizing processes have been
proposed. See, e.g., U.S. Pat. No. 4,392,985 and European Patent
Specification Nos. 0 126 250 and 0 112 667. U.S. Pat. No. 4,392,985
describes that it is advantageous to keep the pH of the impregnating
solution at a value of less than 1.2. EP-B 0 126 250 and EP-B 0 112 667
look to the use of catalysts having a specific, narrow pore size
distribution to obtain the improvement, with EP-B 0 112 667 furthermore
proposing that the use of a group VIII metal be dispensed with. GB 2 055
602 describes catalysts having a comparatively high metals load,
preference being given to nickel and molybdenum. The catalysts are
prepared using a combination of multiple impregnating steps and a shaping
step. This process is a highly specific one and inspired by the thought
that "merely increasing the catalytic metals of any composition can
eventually top out the activity effect and actually begin to give a
decrease in activity at very high metals loadings."
Although more or less acceptable desulphurization results can be obtained
using the catalysts disclosed so far, there is permanent need for improved
catalysts on account of the requirements as to the legally permitted
sulphur content in fuels becoming ever stricter. Equally, this need exists
because at a given final sulphur content a more active catalyst will make
it possible to operate under milder process conditions (energy saving) or
to increase the life span of a catalyst prior to its needing regeneration
(cycle length). Furthermore, this need exists because more and more
additional demands are made on desulphurization catalysts with respect to
their hydrodenitrogenation activity, their life cycle under mild
hydrocracking conditions, and their capacity for producing the lowest
possible olefin content in the end product (improving the colour,
oxidation, and light stabilities).
SUMMARY OF THE INVENTION
The present invention has as its object the provision of a catalyst that
will at least partially satisfy these requirements. It has been found that
this object is attained by using a catalyst equipped with a comparatively
high cobalt and group VIB metal load on the one hand and a comparatively
low phosphorus load on the other. The catalyst according to the invention
contains a porous, inorganic oxidic carrier, a phosphorus component, a
cobalt component, and a Group VIB metal component, wherein, calculated on
100 g of the catalyst composition, the phosphorus component content,
calculated as P.sub.2 O.sub.3, is about 2 to 28 mmoles, the cobalt
component content, calculated as CoO, is about 60 to 133 mmoles, and the
group VIB metal component content, calculated as trioxide, is about 132 to
2os mmoles, the specific surface area of the catalyst composition is
greater than about 100 m.sup.2 g, and the pore volume is in the range of
about 0.25 to 1.3 ml/g. The catalyst preferably consists essentially of
these named components.
DETAILED DESCRIPTION OF THE INVENTION
The catalyst according to the invention contains as carrier material a
porous, inorganic oxide. As examples of suitable materials may be
mentioned alumina, silica, magnesium oxide, zirconium oxide, titanium
oxide, as well as combinations of two or more of these materials.
Preference is given to alumina or alumina combined with silica, i.e.,
silica-alumina in which the amount of silica present may be up to 15
weight percent, preferably up to 10 weight percent, and more particularly
up to 5 weight percent. Most preferred are the so-called transition phase
aluminas (gamma, theta and delta aluminas), in combination with silica or
not. Optimum results are obtained employing carriers containing at least
90 weight percent of transition alumina. Transition aluminas are disclosed
in U.S. Pat. No. 4,154,812 and European Patent EP-B0126250, which are both
incorporated herein by reference. Such materials are also described in
Kirk-Othmer's ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY, Third Ed., Vol. 2, pp.
218-228 (John Wiley & Sons, New York 1978), where the alternative terms
"activated" or "active" alumina are used. This description is also
incorporated herein by reference.
The phosphorus component content in the catalyst, calculated as P.sub.2
O.sub.5, is in the range of from about 2 to about 28 mmoles, preferably 2
to 21 mmoles, calculated on 100 g of catalyst composition. In percentages
by weight these amounts come to about 0.3 to 4 weight percent and about
0.3 to 3 weight percent, respectively. The cobalt component, calculated as
CoO, is present in an amount in the range of from about 60 to about 133
mmoles, preferably about 60 to 93 mmoles, calculated on 100 g of catalyst
composition. In percentages by weight these amounts are about 4.5 to 10
weight percent and about 4.5 to 7 weight percent, respectively. Especially
suited for use are catalysts containing from about 4.5 to 6 weight percent
of cobalt component. Preferred group VIB metals are molybdenum and
tungsten, more particularly molybdenum. The group VIB metal component
content, calculated as trioxide, is in the range of from about 132 to
about 208 mmoles, preferably about 132 to 174 mmoles, calculated on 100 g
of catalyst composition. For, say, molybdenum trioxide these amounts
correspond to percentages by weight of about 19 to 30 weight percent and
about 19 to 25 weight percent, respectively. Preeminently suited to be
used are catalysts containing from about 19 to 23 weight percent of
molybdenum trioxide. For optimum results it is advisable that the ratio of
the number of gram atoms of phosphorus to the sum of the number of gram
atoms of cobalt and group VIB metal should be in the range of from about
0.02 to about 0.25, preferably from about 0.02 to 0.2.
The catalyst should have a specific surface area of at least about 100
m.sup.2 g (B.E.T. method) and a pore volume in the range of about 0.25 to
1.3 ml/g (mercury penetration method; angle of contact 140.degree.).
Preferably, the specific surface area is about 150 to 300 m.sup.2 g and
the pore volume is about 0.3 to 1 ml/g. Also preferably, the catalyst has
a monomodal pore size distribution. The other pore characteristics of the
catalyst may be selected as the feed to be treated requires. For many
catalysts a suitable median pore diameter will be in the range of about 5
to 20 nm, preferably of 5 to 15 nm. The median pore diameter (MPD) is
defined as follows: 50 percent of the pore volume is in pores having a
greater diameter than the MPD and the other 50 percent is in pores having
a smaller diameter than the MPD. Preferred catalysts contain less than 5
percent of their pore volume in pores having a diameter of greater than 25
nm. Still more preferred catalysts contain less than 5 percent of their
pore volume in pores having a diameter of greater than 20 nm. Especially
in the case of feeds substantially made up of components having a boiling
point of 400.degree. C or lower preference is given to the use of
catalysts in which at least 50 percent of the pore volume is in pores
having a diameter in the range of 7 to 9 nm (mercury penetration method).
The catalyst is employed in the conventional manner in the form of spheres
or extrudates. Examples of suitable types of extrudates have been
disclosed in the literature (see, e.g., U.S. Pat. No. 4,028,227). Highly
suitable for use are cylindrical particles (which may be hollow or not) as
well as symmetrical and asymmetrical polylobed particles (having 2, 3 or 4
lobes).
The preparation of catalysts according to the invention may be carried out
in several manners, using techniques known in themselves. Suitable
phosphorus component precursors include phosphoric acid and the various
ammonium hydrogen phosphates. Suitable cobalt component precursors include
cobalt nitrate and cobalt carbonate. Suitable group VIB metal component
precursors include ammonium dimolybdate and ammonium heptamolybdate. Also
suitable for use are the trioxides of the group VIB metals, such as
molybdenum trioxide. These and other P-, cobalt-, or group VIB
metal-containing compounds are known to the person skilled in the art and
will be referred to hereinafter as component precursors (this also applies
to a compound such as molybdenum trioxide). One suitable method of
preparing a catalyst according to the invention is by starting from the
carrier in the preformed condition, such as an extrudate, using an aqueous
solution of the component precursors in question to deposit thereon
suitable amounts of said precursors, e.g. by means of impregnation, and
then, after an optional drying step at a temperature in the range of from
about 25.degree. to about 200.degree. C., calcining the resulting material
at a temperature in the range of from about 350.degree. to about
750.degree. C. to at any rate convert the phosphorus component and metal
component precursors to the desired oxide form.
It will be clear to the person skilled in the art that there can be a wide
number of variations on this method. Thus, it is possible to apply a
plurality of impregnating steps, the impregnating solutions to be used
containing one or more of the component precursors that are to be
deposited, or a portion thereof. Instead of impregnating techniques there
can be used dipping methods, spraying methods, etc. With multiple
impregnation, dipping, etc. drying and/or calcining may be carried out in
between. Alternatively, one or more component precursors can be mixed
wholly or in part with the carrier prior to the shaping step being carried
out. In such an embodiment the component precursor material, or a portion
thereof, can be deposited on the unshaped carrier material, say, a powder,
by means of, e.g., impregnation, after which the shaping step is carried
out. Alternatively, it is possible to intimately mix one or more component
precursors wholly or in part with the carrier material during the shaping
step rather than prior to it. Techniques that are suitable for this
process are co-pelletization and co-extrusion. It is recommended that the
group VIB metal component precursor employed in this process be molybdenum
trioxide.
Optimum results are obtained when care is taken to preclude any or
virtually any reaction between the cobalt component precursor and the
carrier material. Such a reaction will reduce the amount of cobalt that is
effectively available for catalytic ends in the final catalyst. Notably,
when use is made of alumina-containing carriers the prospect of compounds
or complexes containing cobalt and aluminum being formed is undesirable.
Such a reaction can occur when the cobalt component precursor is contacted
with precursors of transition aluminas, such as boehmite, with subsequent
calcining to form the transition alumina. It is therefore recommended to
first subject the transition alumina precursor to a shaping step, e.g.
extrusion, and to subject the resulting carrier to at least one calcining
step, in order to obtain the transition alumina prior to the carrier being
provided with the cobalt component precursor. During this calcination
process, which is generally carried out at a temperature in the range of
about 400.degree. to 1000.degree. C. over a period of 0.5 to 16 hours, in
the presence of steam or not, the transition alumina precursor is
converted into a transition alumina. For an example of the preparation of
a suitable alumina carrier, including the preparation of the transition
alumina precursor (alpha-alumina monohydrate) reference is made to U.S.
Pat. No. 4,154,812.
As described above, to prepare the catalysts of the invention containing
transition alumina(s), one can add the precursors of phosphorus and the
metals (Co and/or Mo) before, during and/or after the shaping of the
chemical precursor(s) of the transition alumina, except that the cobalt
precursor must be deposited after the formation of the transition alumina
(i.e., after calcining).
As indicated hereinbefore, to deposit the component precursors on the
carriers use is generally made of one or more solutions of the component
precursors in water. It has been found that the effectiveness of the final
catalyst can be further enhanced when the aqueous solutions also contain a
compound selected from the group oonsisting of nitric acid, formic acid,
acetic acid, and polycarboxylic acids such as nitrilotriacetic acid,
citric acid, and ethylenediaminetetraacetic acid. Alternatively, salts and
combinations of these compounds can be used. The appropriate amount
depends upon such factors as the nature of the component precursor(s) and
the precursor concentration(s) and is simple to determine experimentally.
Like the prior art hydrodesulphurization catalysts, the catalysts according
to the invention are generally employed in the sulphided form. To this end
use may be made of ex-situ as well as in-situ (pre)sulphidation
techniques. Such methods are well known in the art.
The present catalysts can be used to hydrodesulphurize a wide range of
feeds. Examples of suitable feeds include middle distillates, kerosene,
naphtha, vacuum gas oils, and heavy gas oils, more generally,
hydrocarbon-containing feeds having a metals content (Ni+V) not exceeding
15 ppm, which feeds are substantially (>50% by volume) composed of
components having a boiling point below 600.degree. C., preferably below
400.degree. C. The conventional process conditions, such as temperatures
in the range of about 250.degree. to 450.degree. C., pressures in the
range of 5 to 250 bar, space velocities in the range of 0.1 to 10 hr-1,
and H.sub.2 /oil ratios in the range of about 50 to 2,000 Nl/1, can be
applied here. The present catalysts not only have an excellent
desulphurization capacity, they can also effectively reduce the feed's
olefin content (reduction of the bromine number), thus favorably affecting
the obtained product's colour, light, and oxidation stabilities.
EXAMPLES
The invention will be illustrated with reference to the non-limiting
examples below.
EXAMPLE 1
Preparation of a Catalyst According to the Invention
First, an impregnating solution was prepared. To 3 1 of water of 40.degree.
C. there were added successively, with stirring, 1.18 kg of cobalt
carbonate and 0.45 kg of aqueous phosphoric acid (85%). The suspension had
its temperature increased to and kept for 1 hour at 60.degree. C., after
which 2.74 kg of molybdenum trioxide were added. The temperature was then
increased to and kept for two hours at 96.C, whereupon 476 g of aqueous
nitric acid (65%) were added, after which a clear, stable, reddish-brown
solution was obtained. The total volume of the solution was increased to
6.5 1 by the addition of water, and then the solution was cooled to room
temperature.
Next, 10 kg of .gamma.-alumina (asymmetrical quadrulobe extrudates, 1.2 mm
(short diameter).times.1.4 mm (long diameter); PV(H.sub.2 O): 0.65 ml/g)
were impregnated with the above-described solution. The impregnated
material was allowed to age for 0.5 hours and then dried at 120.degree.
C., first for 1.5 hours in a rotating impregnator and then on a sheet for
24 hours. Finally, the dried material was calcined for 1.5 hours at
530.degree. C. in an air atmosphere. The catalyst had a P.sub.2 O.sub.5
content of 2.0 weight percent, an MoO.sub.3 content of 20.8 weight
percent, and a CoO content of 5.1 weight percent. The pore volume was 0.41
ml/g (mercury penetration method), the surface area 207 m.sup.2 g, and the
median pore diameter 8.0 nm (mercury penetration method).
EXAMPLES 2 TO 11
Examples 2 to 11 below describe the preparation of four catalysts according
to the invention (Examples 2-5) and six catalysts for comparative ends
(Comparative examples 6-11). Example 12 describes how the catalysts of
Examples 1-11 were tested and also lists the results.
In preparing the present catalysts use was made of a carrier in the form of
asymmetrical quadrulobe extrudates [1.2 mm (short diameter).times.1.4 mm
(long diameter)] made up of 98.7 weight percent of .gamma.-alumina and 0.7
weight percent of silica, having a surface area of 290 m.sup.2 /g, and a
pore structure such that the pore volume (Hg) in pores having a greater
diameter than 4.2 nm was 0.58 ml/g and the median pore diameter 6.7 nm
(mercury penetration method). All experimental procedures (preparing the
impregnating solutions, the impregnations, dryings, and calcinations) were
carried out as set down in Example 1, unless otherwise indicated.
EXAMPLE 2
500 g of carrier were impregnated with 325 ml of an aqueous solution
containing 137 g of molybdenum trioxide, 59.2 g of cobalt carbonate, 22.2
g of phosphoric acid (85%), and 34 g of nitric acid (65%). The
impregnating solution was prepared as described in Example 1, except that
the order in which the molybdenum trioxide and the cobalt carbonate were
added was reversed. The composition and properties of the catalyst
obtained after drying and calcination were as listed in Table I below.
EXAMPLE 3
350 g of carrier were impregnated with 230 ml of an aqueous solution
containing 94 g of molybdenum trioxide, 40.6 g of cobalt carbonate, 3.8 g
of phosphoric acid (85%), 29.4 g of nitric acid (65%), and 16 g of citric
acid. The impregnating solution was prepared as described in Example 1,
except that after the nitric acid citric acid was added. The composition
and properties of the catalyst obtained after drying and calcination were
as listed in Table I below.
EXAMPLE 4
1,500 g of carrier were impregnated with 1,000 ml of an aqueous solution
containing 405.3 g of molybdenum trioxide, 175.2 g of cobalt carbonate, 33
g of phosphoric acid (85%), and 142.8 g of nitric acid (65%). The
composition and properties of the catalyst obtained after drying and
calcination were as listed in Table I below.
EXAMPLE 5
1,000 g of carrier were impregnated with 650 ml of an aqueous solution
containing 352.9 g of molybdenum trioxide, 116.0 g of Cobalt carbonate,
72.4 g of phosphoric acid (85%), and 35 g of nitric acid (65%). The
composition and properties of the catalyst obtained after drying and
calcination were as listed in Table I below.
COMPARATIVE EXAMPLE 6
500 g of carrier were impregnated with 325 ml of an aqueous solution
containing 120 g of molybdenum trioxide, 57.6 g of cobalt carbonate, 21.7
g of phosphoric acid (85%), and 25 g of nitric acid (65%). The composition
and properties of the catalyst obtained after drying and calcination were
as listed in Table I below.
COMPARATIVE EXAMPLE 7
500 g of carrier were impregnated with 325 ml of an aqueous solution
containing 134.2 g of molybdenum trioxide, 45.3 g of cobalt carbonate,
33.9 g of phosphoric acid (85%), and 26 g of nitric acid (65%). The
composition and properties of the catalyst obtained after drying and
calcination were as listed in Table I below.
COMPARATIVE EXAMPLE 8
500 g of carrier were first impregnated with 325 ml of an aqueous solution
containing 104.7 g of ammonium dimolybdate (a solution obtained by simply
dissolving the ammonium dimolybdate in water). The material obtained after
drying and calcination (563.4 g) was impregnated with 325 ml of an aqueous
solution containing 155.8 g of molybdenum trioxide, 66.9 g of cobalt
carbonate, 25.2 g of phosphoric acid (85%), and 30 g of nitric acid (65%).
The composition and properties of the catalyst obtained after drying and
calcination were as listed in Table I below.
COMPARATIVE EXAMPLE 9
500 g of carrier were first impregnated with 325 ml of an aqueous solution
containing 149.2 g of molybdenum trioxide, 64.5 g of cobalt carbonate,
24.1 g of phosphoric acid (85%), and 20 g of nitric acid (65%). The
material obtained after drying and calcination (563.4 g) was subsequently
impregnated with 325 ml of an aqueous solution containing 168.5 g of
cobalt nitrate.6H.sub.2 O (a solution obtained by simply dissolving the
cobalt nitrate in water). The composition and properties of the catalyst
obtained after drying and calcination were as listed in Table I below.
COMPARATIVE EXAMPLE 10
500 g of carrier were impregnated with 325 ml of an aqueous solution
containing 142.9 g of molybdenum trioxide, 61.7 g of cobalt carbonate, 58
g of phosphoric acid (85%), and 27 g of nitric acid (65%). The composition
and properties of the catalyst obtained after drying and calcination were
as listed in Table I below.
COMPARATIVE EXAMPLE 11
500 g of carrier were first impregnated with 325 ml of an aqueous solution
containing 157.8 g of ammonium dimolybdate and 2.2 g of phosphoric acid
(85%). The material obtained after drying and calcination (618 g) was
impregnated with 325 ml of an aqueous solution containing 126.6 g of
cobalt nitrate.6H.sub.2 O. The composition and properties of the catalyst
obtained after drying and calcination were as listed in Table I below. The
two impregnating solutions used in this example were prepared by simply
dissolving the components in question in water.
EXAMPLE 12
The catalysts were compared with each other with respect to their
desulphurization capacity. The techniques and equipment used in this
process have been described in detail in Applied Catalysis Vol. 43, pp.
239 ff (1988); Ind. Eng. Chem. Process Des. Dev. Vol. 20, pp. 40 ff
(1981); and Proc. 6th Int. Congr. Catal. Vol. 2, London 1976 (eds. G. C.
Bond et al.), paper B34. The procedure was as follows.
Use was made of a Kuwait Straight Run Gas Oil having the following
specification:
______________________________________
density at 50.degree. C.:
0.8145 g/ml
sulphur content: 1.175 weight percent (S)
nitrogen content: 92 ppm (N)
ASTM D86 distillation data:
IBP: 177.degree. C.
50 vol. %: 288.degree. C.
FBP: 365.degree. C.
______________________________________
The catalyst was charged to a reactor and first sulphided. To this end the
gas oil, into which 2.5 weight percent of dimethyl disulphide (spiking
agent) had been incorporated, was passed through the catalyst bed for 3
hours at a temperature of 100.degree. C., a pressure of 30 bar (no H.sub.2
flow), and an LHSV of 4.0 hr.sup.-1 (pre-wetting), after which over a
period of 8 hours the temperature was gradually increased to 320.degree.
C. During this increase in temperature the LHSV was 1.0 hr.sup.-1, the
pressure continued to be 30 bar, and an H.sub.2 flow was started up:
H.sub.2 /oil ratio 120 Nl/1. The situation at 320.degree. C. was
maintained for 10 hours, after which the sulphidation process was
completed. Next, the spiked gas oil was replaced with the gas oil itself
and the following test conditions were successively imposed:
______________________________________
LHSV H.sub.2 /Oil
Pressure
Temperature
Test condition
hr.sup.-1
N1/1 bar .degree.C.
______________________________________
1 3.00 120 30 335
2 2.00 120 30 335
______________________________________
After dissolved H.sub.2 S and NH.sub.3 had been removed from the product
streams (by passage of N.sub.2), the sulphur contents of the products were
determined by means of X-ray fluorescence spectroscopy (XRF) in accordance
with ASTM D2622. The data obtained were used to calculate the relative
volume activity (RVA), with test results obtained with the same volume of
a commercially available HDS catalyst (KF-742.RTM. ex Akzo Chemicals;
chemical composition: 15.0 weight percent of MoO.sub.3, 4.0 weight percent
of CoO, alumina carrier; SA: 270 m.sup.2 /g; PV(Hg): 0.52 ml/g; MPD: 8.0
nm) being employed as a reference.
First, the reaction speed constant k was calculated:
##EQU1##
where Sprod is the sulphur content of the product and Sfeed is the sulphur
content of the feed, each expressed in weight percent.
The reaction order n was determined by means of iteration, k having the
same value under the two test conditions. In order to compensate for
differences in n for the various catalysts the LHSV for 92 percent HDS
conversion was calculated:
##EQU2##
The results are listed in Table I below. They show that the catalysts
according to the invention were substantially more active than the
comparative catalyst.
TABLE I
__________________________________________________________________________
Catalyst properties
per 100 g of composition
MoO.sub.3 CoO P.sub.2 O.sub.5
mmole
mmole
mmole
SA PV MPD % PV > RVA
Example
(wt. %)
(wt. %)
(wt. %)
m/g
ml/g
nm 20 nm.sub.d
__________________________________________________________________________
1 144 68 14 207
0.41
8.0 2.9 126
(20.8)
(5.1)
(2.0)
2 142 68 13 193
0.40
8.2 2.6 123
(20.5)
(5.1)
(1.9)
3 147 67 3.3 235
0.42
7.6 4.3 126
(21.2)
(5.0)
(0.47)
4 143 67 7 210
0.41
8.2 3.3 130
(20.6)
(5.0)
(1.0)
5 171 67 21 169
0.37
8.2 1.9 118
(24.6)
(5.0)
(3.0)
6* 124 65 13 206
0.43
8.0 3.0 99
(17.8)
(4.9)
(1.8)
7* 144 53 21 201
0.41
8.0 ** 99
(20.7)
(4.0)
(3.0)
8* 212 68 15 143
0.31
7.6 3.3 97
(30.6)
(5.1)
(2.1)
9* 127 148 15 185
0.37
7.6 4.2 83
(18.3)
(11.1)
(2.1)
10*
144 68 33 193
0.39
7.4 ** 103
(20.7)
(5.1)
(4.7)
11* 137 68 1.4 217
0.42
7.8 4.0 89
(19.7)
(5.1)
(0.2)
__________________________________________________________________________
*comparative example
**not available
SA=Specific Surface area, PV=Pore volume, MPD=Median Pore Diameter (as
referred to on page 5 lines 32 to 35), RVA=Relative Volume Activity (as
referred on page 18, lines 22 to 24 and page 16, line 7) and %PV>20
nm.sub.d means the percentage of the pore volume in pores having diameters
greater than 20 nm.
EXAMPLE 13
This Example illustrates the effectiveness of the catalysts according to
the invention in deep hydrodesulphurization. The catalyst of Example 2 was
compared with the commercially available KF-742.RTM. HDS catalyst
mentioned in Example 12. The test procedure was the same as that described
in Example 12, except for the feedstock and the test conditions. The
feedstock was a partially desulphurized Kuwait Straight Run Gas Oil having
a density at 50.degree. C. of 0.8081 and a sulphur content of 0.165 weight
percent. The test conditions were as follows:
______________________________________
LHSV H.sub.2 /Oil
Pressure
Temperature
Test condition
hr.sup.-1
N1/1 bar .degree.C.
______________________________________
1 1.5 120 30 375
2 3.0 120 30 375
______________________________________
After dissolved H.sub.2 S and NH.sub.3 had been removed from the product
streams, the sulphur contents of the products were determined by means of
XRF in accordance with ASTM D2622. The data obtained was used to calculate
the relative volume activity (RVA) in the same manner as described in
Example 12, albeit that to compensate for differences in reaction order n
for the two catalysts the LHSV in this case was calculated at a constant
conversion for 98 percent HDS. It was found that the RVA, being equal to
##EQU3##
was 161.
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